This is a Phase II, randomized, study of two dose schedules of IDV and DMP-266 with or without 1592U89 in subjects who have received ZDV (or d4T)/3TC. Approximately 300 NNRTI naive subjects will be enrolled in this study. Study subjects randomized to the ZDV (or d4T)/3TC arm of ACTG 320, who are PI naive and still receiving ONLY ACTG 320 double nucleoside study medications are eligible for enrollment. In addition, subjects not participating in ACTG 320 with HIV infection who have had > 3 months of therapy with ZDV (or d4T)/3TC and no prior NNRTI or protease inhibitor therapy and are receiving ZDV (or d4T)/3TC at the time of randomization will also be considered for enrollment. Subjects with > 50 CD4 cells/mm3 will be randomized to one of four treatment arms and followed for 48 weeks beyond the enrollment of the last subject. Subjects with 50 CD4 cells/mm3 will be randomized to one of two treatment arms (Arms I and II) and will be followed for 48 weeks beyond the enrollment of the last subject. Non-ACTG 320 volunteers are required to have had a documented CD4 cell count 200/mm3 at the time of initiation of ZDV (or d4T) plus 3TC. ACTG 320 subjects who had documented NNRTI experience at randomization to ACTG 320 and who have approval from the Protocol Chair/Vice Chairs, will be assigned at entry to receive an open-label regimen of IDV 1000 mg TID + DMP-266 600 mg qd + 1592U89 300 mg BID. Sufficient slots will be reserved for ACTG 320 rollover subjects.